1. Field of the Invention
The present invention relates to a semiconductor device including an interconnect insulating film constituted of a low dielectric constant film and to a method of manufacturing the same, more specifically to a semiconductor device including a concentrated region where a plurality of interconnects is closely formed, and to a manufacturing method thereof.
2. Description of the Related Art
Recent progress in micronization and in operating speed of a semiconductor device has made it indispensable to employ so-called a low dielectric constant film in combination with a copper interconnect. As a method of forming a copper interconnect, Damascene process is generally employed, which basically consists of forming an interconnect trench in an interconnect insulating film, burying copper in the trench, and removing surplus copper outside the trench by CMP (chemical mechanical polishing) process (JP-A laid open 2001-176965).
However the Damascene process has a drawback that a part of the interconnect insulating film is also removed by CMP method performed after burying copper, because of which interconnect resistance increases or becomes unstable. Generally a low dielectric constant film has lower chemical resistance and less mechanical strength than an SiO2 film conventionally used as an interconnect insulating film. Accordingly, an interconnect insulating film made of a low dielectric constant material is more prone to be scraped off by CMP than that made of an SiO2 film.
This problem will be described in detail referring to FIGS. 1A and 1B. In FIG. 1A, on a lower insulating layer 1 an etch-stopper film 2 made of for example an SiN film is formed, over which an interconnect insulating film 3, for example made of an HSQ film, is formed. On the interconnect insulating film 3, a barrier film 5 constituted of for example Ta, TaN, Ti, TiN or layers thereof, and an interconnect 4 constituted of an interconnect metal film 6 such as Cu are formed. On the interconnect insulating film 3 and the interconnect 4 an insulative etch-stopper film 7 made of for example an SiN film is formed, on which an interlayer insulating film 8 of for example SiO2 is formed, and further on the interlayer insulating film 8 another etch-stopper film 9 of for example SiN, and then another interconnect insulating film 10 made of for example an HSQ film is formed on the etch-stopper film 9. On these films 7 to 10, another barrier film 12 constituted of for example Ta, TaN, Ti, TiN or multiple layers thereof, and a via and an interconnect made of an interconnect metal film 13 such as Cu are formed.
Under the Damascene process, an excess of the interconnect metal film 13 and of the barrier film 12 deposited on the interconnect insulating film 10 are removed by CMP method. Here, an HSQ film having a cage-type molecular structure may be cited as an example of a low dielectric constant material having a dielectric constant not greater than 3.6. However, in the event of employing the HSQ film as an interconnect insulating film, the film is largely scraped off during a CMP process of removing an excess of the interconnect metal film 13 and so on, because of the lack of chemical resistance and mechanical strength. Consequently, in case where HSQ is used as the interconnect insulating film 11, a considerable portion of the interconnect insulating film 11 is removed especially in a concentrated region where the interconnects are closely formed, and an extensive erosion region 14 is formed as shown in FIG. 1B.